JP3337414B2 - Radial tires for heavy loads - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty radial tire which can be suitably used as an all-season tire and has improved running performance on shallow snow without deteriorating wear resistance.

[0002]

2. Description of the Related Art In recent years, all-season tires that travel on, for example, a snowy road while maintaining high-speed running performance have been frequently used.

In general, this type of tire has a sea ratio, which is a ratio of the total area S1 of the vertical main grooves and the horizontal grooves to the area S of the tread contact area, in order to achieve both abrasion resistance and performance on shallow snow. A block pattern in which S1 / S is increased to about 0.35 is employed. In this block pattern, the edges of the vertical main groove and the lateral groove are mainly used to secure the grip performance on the shallow snow by the shearing force (snow column shearing force) received from the snow column which is bitten into the lateral groove and compacted. The lateral edge density E, which is the ratio A / S of the total length A of the lateral edge components to the area S of the ground region, is set to about 0.024.

[0004] However, in this case, since the lateral edge density E is relatively low, the lateral grooves tend to be wide, and there is a problem that traction on snow is insufficient, although the snow removal is excellent. When the lateral edge density E is increased, the traction on snow can be supplemented by the edge effect, but on the other hand, the block rigidity is insufficient, the wear resistance is impaired, and uneven wear and chipping of the block are induced. .

On the other hand, by reducing the sea ratio S1 / S, the block rigidity is increased. In particular, the sea ratio S1 / S is 0.3
When the value is reduced to 0 or less, it becomes possible to increase the lateral edge density E to about 0.035 while securing the necessary wear resistance. At this time, the decrease in the shearing force of the snow column due to the low sea ratio S1 / S is compensated for by the edge effect, so that the traction on snow is maintained. However, there is a problem that the snow removal performance is deteriorated and clogging is likely to occur.

[0006] As described above, only by optimizing the sea ratio S1 / S and the lateral edge density E, it is possible to prevent uneven wear and lack of blocks due to insufficient rigidity without impairing abrasion resistance. It was difficult to improve snow removal and traction at the beach.

Therefore, the present invention provides a sea ratio S1 / S of 0.26.
~ 0.34, and the lateral edge density E is 0.025 ~
The wear resistance is basically controlled by setting the lateral edge density Es in the outer tangent region to 0.60 to 0.85 times the lateral edge density Ec in the central tangent region while regulating to 0.035. It is an object of the present invention to provide a heavy-duty radial tire capable of improving snow removal performance and traction on shallow snow without impairing and preventing uneven wear and chipping due to insufficient rigidity.

[0008]

In order to achieve the above-mentioned object, the present invention relates to a method for manufacturing a vehicle comprising four vertical main members extending continuously in a circumferential direction on a tread surface and having a groove width of not less than 3.0 mm and not more than 19.0 mm. By providing a groove and a horizontal groove intersecting the vertical main groove, the tread surface is formed by a pair of shoulders composed of a central block row composed of blocks arranged in the circumferential direction on the tire equator and a block composed of blocks arranged in the circumferential direction along the tread edge. Block column,
And a radial tire for heavy load divided into a pair of intermediate block rows composed of blocks arranged in the circumferential direction between the center block row and the shoulder block row, wherein the vertical main groove has a groove width of 7.0 mm or more. The distance L from the groove center of the longitudinal main groove outside the tire axial direction to the tire equator, including two or more wide vertical main grooves, was set on a standard rim, filled with a standard internal pressure, and loaded with a standard load. In the standard state, the width TW of the contact area where the tread surface contacts the ground is 0.2.
The lateral groove forming the intermediate block row is 5 to 0.35 times, and the lateral groove forming the intermediate block row is composed of an arcuate lateral groove having a circular arc center in the intermediate block row, and the ground area is smaller than the area S of the ground area. The sea ratio S1 / S, which is the ratio of the total sum S1 of the groove areas of the vertical main groove and the horizontal groove, is 0.26 to 34, and the edge portion formed by the groove edges of the vertical main groove and the horizontal groove arranged in the ground area Is the ratio A / S of the total length A of the lateral edge components of the above to the area S of the ground region, and the lateral edge density E
0.025 to 0.035 (unit: mm / mm ² ) In addition, the lateral edge density Ec in the central contact area between the groove centers of the outer vertical main grooves in the ground contact area, and the outside of this central contact area The edge density ratio Es / Ec with respect to the lateral edge density Es in the outer bordering area is 0.60 to 0.60.
0.85.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a heavy duty radial tire 1 (hereinafter referred to as a tire 1) is an all-season tire having a tire size of 11R22.5 in this example, and has bead portions 3, 3 on both sides through which a bead core 2 passes, and each bead portion. 3 includes a sidewall portion 4 extending outward in the tire radial direction, and a tread portion 5 extending between upper ends thereof. A carcass 6 is bridged between the bead portions 3, and a belt layer 7 is wound around the carcass 6 and in the tread portion 5 in the circumferential direction.

The carcass 6 is formed of one or more carcass plies in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C. Then, the bead portion 3 is folded inward and outward around the bead core 2 of the bead portion 3 and locked. As the carcass cord, an organic fiber cord made of nylon, polyester, rayon, aromatic polyamide fiber or the like, or an inorganic fiber cord made of steel fiber or the like can be used. In this example, the carcass 6
Shows a steel carcass cord formed from one carcass ply in which carcass cords are arranged at an angle of about 90 °.

The belt layer 7 includes a plurality of belt plies,
In the present example, the innermost first belt ply 7A in which a steel belt cord is inclined at a cord angle of about 60 ± 10 ° with respect to the tire equator C, and a belt cord with respect to the tire equator C, for example. The second to fourth belt plies 7B, 7C and 7D are inclined at a small cord angle of 30 ° or less, and the cord angles or the inclination directions of the cords are changed so that the belt cords cross each other between the plies. I overlap.

As shown in FIG. 2, the tread surface 5S, which is the outer surface of the tread portion 5, extends continuously in the circumferential direction and has a groove width Wg of 3.0 to 19.0 mm. When,
A block pattern divided by the horizontal groove Y intersecting with the vertical main groove G is formed.

The vertical main groove G is composed of four vertical main grooves G1 disposed on both sides of the tire equator C and an external vertical main groove G2 disposed outside thereof. Two,
In this example, all four grooves are formed as wide substantially straight grooves having the groove width Wg of 7.0 mm or more.

The vertical main groove G may be formed as a zigzag groove other than a straight groove, or may be formed by changing the groove width Wg. In such a case, both the minimum width and the maximum width are in the range of 3.0 to 19.0 mm and in the range of 7.0 to 19.0 mm.

The horizontal groove Y includes a central horizontal groove Y1 crossing between the vertical main grooves G1, G1, an intermediate horizontal groove Y2 crossing between the vertical main grooves G1, G2, and the vertical main groove G2 and a tread edge Te. And a lateral groove Y3 on the side crossing the gap. This lateral groove Y
Is at least wider than the siping 10, i.e., the groove width Wy is 2.0 mm or more, and the groove depth is 0.7 to 1.0 times the groove depth of the vertical main groove G, in this example , 1.0 times to improve wet performance and snow performance. The lateral groove Y partially forms a shallow bottom Ya (shown in FIG. 1) protruding from the bottom of the groove, and connects the blocks in the circumferential direction at the shallow bottom Ya to increase the block rigidity.

In the present embodiment, the central horizontal groove Y1 is inclined substantially linearly at an angle of 60 degrees or less, for example, about 40 degrees with respect to the tire axial direction, and cooperates with the vertical main grooves G1, G1. To form a central block row R1 composed of blocks B1 arranged in the circumferential direction on the tire equator.

The intermediate horizontal groove Y2 is provided with the vertical main groove G1,
Between G2, it forms a circular arc shape having a circular arc center. The lateral groove Y2 may be formed by a single curved line, a compound curve composed of a plurality of circular arcs, or a compound curve composed of a circular arc and a straight line. However, from the viewpoints of circumferential rigidity, snow removal properties, traction properties, etc., it is preferable that 70% or more of the length of the lateral groove Y2 in the tire axial direction be formed by a single arc as in this example,
At this time, the radius of curvature of the arc is preferably 0.5 to 1.0 times the length of the lateral groove Y2 in the tire axial direction. The arc-shaped groove is also useful for suppressing heel & toe wear and the like. Also, the horizontal groove Y2 cooperates with the vertical main grooves G1 and G2 to form a block B2 adjacent to the central block row R1 and arranged in the circumferential direction.
Is formed.

The lateral groove Y3 extends at a smaller inclination angle than the central lateral groove Y1, in this example, substantially parallel to the tire axial direction, and cooperates with the vertical main groove G2 and the tread edge Te.
A pair of shoulder block rows R3 composed of blocks B3 arranged in the circumferential direction along the tread edge Te are formed.

The outer vertical main groove G2 is formed at a position where the distance L between the groove center N and the tire equator C is 0.25 to 0.35 times the width TW of the ground contact area P. The ground area P is formed by the outer vertical main grooves G2 so that the center of the grooves N, N
The central contact area Pc that is between and the outer contact area Ps outside the central contact area Pc
And divided into

The ground contact region P is defined as a width region where the tread surface 5S contacts the tire 1 in a standard state in which the tire 1 is assembled on a standard rim, a standard internal pressure is applied, and a standard load is applied. The standard rim is JA
The rim specified by the standard such as TMA, the standard internal pressure means the maximum air pressure specified by the standard, and the standard load means the maximum load capacity specified by the standard. In this example, the tread portion 5 forms a tapered shoulder having an inclined surface disposed between the tread edge Te and the buttress surface Bs, and the entire region of the tread surface 5S forms the ground contact region P.

Here, in the ground area P, the sea ratio S1 / S, which is the ratio of the area S of the ground area P to the sum S1 of the groove areas of the vertical main groove G and the horizontal groove Y arranged in the ground area P, is as follows:
It is regulated to 0.26 to 0.34.

Further, the lateral edge density in the ground area P is regulated as follows. That is, the lateral edge density E in the entire ground region P is set to 0.025 to 0.025.
0.035 (unit: mm / mm ² ), and the edge density ratio Es / Ec between the lateral edge density Ec in the central contact area Pc and the lateral edge density Es in the outer contact area Ps is set to 0. .60-0.
The range is 85.

The lateral edge density E refers to the total length A of the lateral edge components of the edges formed by the vertical main groove G and the horizontal groove Y disposed in the ground area P, and the lateral edge density of the ground area P. It is defined as the ratio A / S to the area S. In other words, the block B surrounded by the horizontal groove Y, the vertical main groove G and the tread edge Te as shown in FIG.
Can be said to be a total length ΣΣei of the lateral edge component length Σei obtained by projecting the edge e formed by the peripheral edge in the tire axial direction with respect to all the blocks B in the ground contact area P. When the block B is located over the inside and outside of the ground area P, an edge portion outside the ground area P is excluded.

Further, the lateral edge density Ec in the central contact area Pc is obtained by calculating the total length Ac of the lateral edge components of the edge portions formed by the vertical main grooves G and the horizontal grooves Y arranged in the central contact area Pc, Ratio A to area Sc of central contact area Pc
Similarly, the lateral edge density Es in the outer tangent area Ps is defined as the sum of the lateral edge components of the edge portions formed by the vertical main groove G and the lateral groove Y in the outer tangent area Ps. It is defined as the ratio As / Ss between the length As and the area Ss of the outer contact area Ps.

Here, the outer contact area Ps is an area where the contact pressure is higher than that of the central contact area Pc and where a large external force (lateral force) is applied particularly at the time of turning. It is easy to wear due to slip with the road surface.

Therefore, the sea ratio S1 / S is set to 0.26-0.3.
4 and the total lateral edge density E is 0.025.
While maintaining the range of ~ 0.035, the lateral edge density Es of the outer tangent area Ps is set to a predetermined ratio (0.60 to 0.85) from the lateral edge density Ec of the central tangent area Pc.
Has been reduced.

Thus, the shoulder block row R3
The rigidity of the block is appropriately increased, and uneven wear and chipping of the block can be suppressed. In addition, since the outer contact area Ps has a relatively high contact pressure, the shear strength of the snow column functions more effectively by increasing the block rigidity, and the snow removal and traction can be improved.

On the other hand, in the central contact area Pc, since the contact pressure and the external force are relatively small, the lateral edge density Ec
And block wear can be suppressed even when the block rigidity is reduced. Further, since the contact pressure is low, it is effective for the function of the edge effect. By increasing the lateral edge density Ec, the edge effect can be maximized and the traction can be improved. Moreover, since the contact pressure is low, the compaction of snow in the lateral groove Y is weak, and clogging is unlikely to occur.
Snow removal performance can be kept good to some extent.

As described above, in the limited sea ratio S1 / S and the total lateral edge density E, the lateral edge densities Ec and Es are changed according to the characteristics of the central contact area Pc and the outer contact area Ps. As a result, it is possible to improve snow removal and traction on shallow snow without impairing wear resistance and preventing uneven wear and block chipping.

If the sea ratio S1 / S is less than 0.26, the snow removal property cannot be improved, and if it exceeds 0.34, the wear resistance cannot be improved. If the total lateral edge density E is less than 0.025, the traction property is not improved, and if it exceeds 0.035, the block lacking performance is lacking and the steering stability on a dry road surface is insufficient. When the edge density ratio Es / Ec is less than 0.60, the traction properties are insufficient.
In particular, uneven wear resistance and block chipping performance in the shoulder block row R3 are insufficient.

The blocks B1, B2, and B3 include:
In order to enhance the performance on ice, a sipe 10 having a groove width of less than 2.0 mm can be provided. In this example, a sipe 10A that crosses the block B1 almost in parallel with the lateral groove Y1 is provided in the block B1. . The block B2 includes a sipe 10B that crosses the block B2 in the circumferential direction at a position close to the vertical main groove G2, and a sipe 10B and the vertical main groove G1.
And a sipe 10 extending in an arc shape substantially parallel to the lateral groove Y2.
C is arranged.

At both ends of the tread surface 5S, a tread edge T
A vertical narrow groove 11 having a groove width of less than 3.0 mm extending in the circumferential direction is arranged in proximity to e to prevent uneven wear due to shoulder drop and enhance wandering performance.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure of FIG.
2.5 A 14R tire was prototyped based on the specifications in Table 1, and the wear resistance, uneven wear resistance, block chipping resistance, traction on snow, steering stability and snow removal of each test tire were tested. These were compared. Each of the test tires basically had the same pattern as the tread pattern of FIG. 2, and the sea ratio and the lateral edge density were changed by changing the number of lateral grooves and the width of the lateral grooves.

The abrasion resistance, uneven wear resistance and block chipping resistance are as follows. A sample tire having a rim assembled to a rim of 7.50 × 22.5 and filled with an internal pressure of 800 kpa is loaded on a 2-D · D vehicle (loading load). Attached to all wheels (10 ton load), run on a dry asphalt road surface for a distance of 50,000 km in a constant load condition, and determine the amount of wear, uneven wear, the number and size of chipped blocks after running (good). , △ (normal), × (impossible).

The steering stability was evaluated in terms of 官能, Δ, and × by a sensory evaluation of the driver in terms of steering wheel responsiveness, rigidity, grip, and the like during running.

The traction on snow was evaluated by using the above-mentioned vehicle equipped with new test tires, traveling on a shallow snowy road (depth of snow 30 mm) in a constant-volume state, and performing sensory evaluation of ○, Δ, and ×. The evaluation was made in three steps.

The snow removal performance was evaluated by observing snow clogging when traveling on the above-mentioned shallow snow road by visual observation from the outside of the vehicle.
The evaluation was made in three stages of Δ and X.

[0038]

[Table 1]

As shown in Table 1, Examples 1 to 5 in which the sea ratio S1 / S, the lateral edge density E, and the edge density ratio Es / Ec satisfy the ranges of the present application, have the abrasion resistance, uneven wear resistance,
Block chipping resistance, traction on snow, steering stability,
It can be seen that each of the snow removal properties can be maintained at a desirable level.

[0040]

As described above, according to the present invention, the sea ratio S1 / S is set to 0.26 to 0.34, and the lateral edge density E is set to 0.
Since the lateral edge density Es in the outer contact area is set to a range of 0.60 to 0.85 times the lateral edge density Ec in the central contact area while regulating to 025 to 0.035, wear resistance is improved. The snow removal performance and the traction performance on shallow snow can be improved without impairing the performance and preventing uneven wear and chipping due to lack of rigidity.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a developed view showing the tread pattern.

FIG. 3 is a plan view of a block for explaining a lateral edge component.

[Explanation of symbols]

 5S Tread surface B, B1, B2, B3 Block G, G1, G2 Vertical main groove N Groove center of vertical main groove outside P Grounding area Pc Center contact area Ps Outside contact area R1 Central block row R3 Shoulder block row R2 Intermediate block Row Te Tread edge Wg Groove width of vertical main groove Y, Y1, Y2, Y3 Horizontal groove

Claims (1)

(57) [Claims] (1) By providing four longitudinal main grooves extending continuously in the circumferential direction and having a groove width of 3.0 mm or more and 19.0 mm or less on a tread surface, and a horizontal groove intersecting with the vertical main grooves.
The tread surface is circulated between the center block row composed of blocks arranged in the circumferential direction on the tire equator, a pair of shoulder block rows composed of blocks arranged in the circumferential direction along the tread edge, and the center block row and the shoulder block row. A radial tire for heavy load divided into a pair of intermediate block rows composed of blocks arranged in a direction, wherein the vertical main groove includes two or more wide vertical main grooves having a groove width of 7.0 mm or more, and a tire. The distance L from the groove center of the axially outer vertical main groove to the tire equator is the width of the contact area where the tread surface contacts the ground in a standard state where the rim is assembled to a standard rim, a standard internal pressure is applied, and a standard load is applied. T
W is 0.25 to 0.35 times W, and the horizontal groove forming the intermediate block row is formed by a circular horizontal groove having an arc center in the intermediate block row, and the ground area is the ground area. Sea ratio S1 / which is the ratio of the sum S1 of the groove area of the vertical main groove and the horizontal groove to the area S of
S is 0.26 to 0.34, and the total length A of the lateral edge components of the edges formed by the vertical main groove and the horizontal groove arranged in the ground region and the area S of the ground region The lateral edge density E, which is the ratio A / S, is 0.025 to 0.035 (unit: mm / mm ² ). In addition, the lateral edge in the central contact area between the groove centers of the outer vertical main grooves in the ground contact area. The edge density ratio Es / Ec between the density Ec and the lateral edge density Es in the outer contact area outside the central contact area is 0.60 to 0.60.
A heavy-duty radial tire characterized by being 0.85.